There are features in the interface for commenting on the variant unit and a link that will take you to the local stemma and coherence modules for said variant unit. There is also an option to see the unedited collation data, a list of patristic citations (fuller than in the print edition as I understand it), the Vetus Latina collations, and a nice feature which tells you how many conjectures have been offered for the variant unit and a link that will take you to the data in the Amsterdam Database of New Testament Conjectural Emendation.
To access the text, see INTF’s virtual manuscript room. Although ECM is itself available also for the synoptics’ parallel passages and the catholic letters, the online version currently includes only the Acts material.
For additional discussion and a short video clip from the occasion, see Peter Gurry’s original post.